Spider mites are not harmful to humans. These mites, which are related to spiders and ticks, specifically feed and reproduce on plants, so the pests are not able to use humans for these purposes.
Spider mites do harm vegetation. Plant leaves are a food source for spider mites, and they sometimes damage foliage. Excessive feeding causes leaves to turn yellowish or reddish and fall off plants. This sometimes impacts the production of fruit. Fruit trees yield less produce if they lose their leaves in spring or early summer. Annual crops, such as squash and melons, are more significantly effected by leaf loss. In addition, spider mites eat pods on bean and pea plants and limit the harvest.